Field of the Invention
The present invention relates to an image forming apparatus including a copier, a printer, and a FAX.
Description of the Related Art
In order to achieve low power consumption for environmental friendliness, it is necessary to suppress power consumption in a heating member of a fixing device that consumes relatively a large amount of power on an image forming apparatus. In recent years, measures for achieving a lower fixing temperature and a fixing member with lower heating capacity are increasingly implemented.
Patent Literatures that disclose techniques to suppress power consumption of the image forming apparatus include, for example, JP 2008-249813 A and JP 2012-016903 A.
On an image forming apparatus, energy consumption needed to increase the temperature of a heating member to a target temperature changes depending upon factors that vary over time, such as a heat storage state of a fixing device and a temperature of a recording material, and factors related to a heating value, such as thickness of the recording material.
Therefore, it is necessary, on each of print modes, to maintain a level of the energy consumption desired by a user, or below, while maintaining a predetermined range of fixability in each of print modes. To achieve this, it is necessary to perform control so as not to exceed prescribed integrated energy consumption per unit time, while considering the heat storage state of the fixing device, thickness of the recording material, a temperature of the recording material, or the like.
JP 2008-249813 A discloses control of instantaneous power consumption to a predetermined upper limit or below. However, control of energy consumption during execution for each of modes to a predetermined upper limit or below is not disclosed.
Specifically, in JP 2008-249813 A, a temperature of a fixing roller is controlled based on power consumption conditions, namely, conditions on power that can be consumed at image forming, and based on a result of detection by a temperature detection element. More specifically, when assuming power consumption (W) in a control system to be W1% of the total, power consumption (W) in a drive system to be W2% of the total, and power consumption (W) in a fixing system to be W3%, the temperature of the fixing roller at image forming is controlled by allocating power consumption (W) in the fixing system from a sum of available power consumption (W) based on this W3, which is calculated by W3=100−(W1+W2). This technique, however, cannot control energy consumption (Wh), namely, power consumption (W)×operation time (h), because the operation time (h) changes depending on print mode conditions such as the number of printed sheets.
Meanwhile, JP 2012-016903 A discloses a technique related to energy consumption. JP 2012-016903 A discloses a technique of selecting an operation mode at printing such that the energy consumption does not exceed the upper limit set for a predetermined period (e.g. one month).
In this, however, the upper limit of energy consumption is not set for each of modes, and there is no technique disclosed related to controlling an energization ratio at fixing for individual modes so as not to exceed the set upper limit of energy consumption.
Specifically, in JP 2012-016903 A, energy consumption for executed individual modes is stored, and accumulated energy consumption is compared with the energy consumption for a predetermined period (e.g. one month). In a case a difference is small, an operation mode with smaller energy consumption is selected, and a next mode is then printed.
As described in paragraph 0018 of JP 2012-016903 A, power consumption differs depending on print conditions even in a same operation mode. It is, thus, not possible to change image forming process conditions for each of modes. Accordingly, it is difficult to achieve “maintaining the energy consumption level desired by a user, or below, while maintaining a predetermined range of fixability in each of print modes”.